In the manufacture of containers, various anomalies or variations can occur that affect the commercial acceptability of the containers. These anomalies, termed “commercial variations,” can involve one of numerous attributes of the container. For example, commercial variations can include dimensional characteristics of the container at an open mouth of the container. Thus, it is often times useful to provide inspection equipment capable of inspecting the containers for commercial variations. The term “inspection” is used in its broadest sense to encompass any optical, electro-optical, mechanical or electrical observation or engagement with a container to measure or determine a potentially variable characteristic, including but not necessarily limited to commercial variations.
FIG. 21 illustrates in simplified and diagrammatic form an apparatus 810 for inspecting parameters of a container mouth 812 in one type of inspection process for a container 814 that generally conforms to an apparatus shown and described in U.S. Pat. No. 5,461,228, which is assigned to the assignee hereof and is incorporated herein by reference. The apparatus 810 includes a light source 818 that directs light into the container 814, and a light sensor 824 disposed with respect to the light source 818 and the container 814 to receive light transmitted out of the container 814 through the container mouth 812. A telecentric lens 822 directs onto the light sensor 824 only light transmitted through the container mouth 812 substantially axially of the container mouth 812. The sensor 824 develops a two-dimensional image of the container mouth 812. The sensor 812 is coupled to image processing electronics (not shown) for determining or calculating a circle of greatest diameter that will fit within the two-dimensional image of the container mouth 812, and treating such circle as indicative of the effective inside diameter of the container mouth 812.
The container 814 may include commercial variations like choke portions 813 that may block some light rays 815 and reflect other, angled, light rays 817 in a direction generally parallel with the container longitudinal axis. The sensor 824 senses not only unimpeded light rays 819 that indicate the inside diameter of the container mouth 812, but also the reflected light rays 817, which tend to make the container mouth 812 appear larger than it really is. Accordingly, as shown in prior art FIG. 22, a prior art light image produced by light from the light source of FIG. 21 includes a pattern of bright unimpeded light 819′ representing the inside diameter of the mouth 812 and a halo or additional pattern of reflected light 817′ representing the reflections off the inside diameter of the mouth 812.
A general object of the present disclosure, in accordance with one aspect of the disclosure, is to provide a more reliable optical plug gage (OPG) apparatus for gaging a container mouth to reduce or eliminate reflected light in an OPG image, and/or to prevent passage of certain light rays reflected from an inside surface of a container mouth in a direction parallel to a container axis to a light sensor so that the container mouth does not appear larger than actual size.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
An apparatus for inspecting a container having a base and a mouth in accordance with one aspect of the disclosure includes a light source for directing light through the container base into the container, and out of the container through the container mouth. The apparatus also includes a light sensor disposed with respect to the light source and the container to receive light transmitted through the container mouth. The light source includes at least first and second light sources operatively disposed adjacent to each other beneath the container base and having differing operating characteristics.
In accordance with another aspect of the disclosure, there is provided a method of inspecting a container having a base and a mouth, including the step of directing light through the container base into the container, and out of the container through the container mouth, using at least first and second light sources operatively disposed adjacent to each other beneath the container base and having differing operating characteristics. The method also includes the step of sensing light transmitted through the container mouth.